The loading of substances such as flavours or fragrances into microcapsules is well known to the art. In a typical process, there are provided blank capsules comprising a hydrogel shell and an oily interior. These capsules are loaded with the desired substance by immersing them in an aqueous solution of the substance to be loaded for sufficient time for loading to take place. The water allows the transport of the substances through the water-containing hydrogel shell into the oil core by aqueous diffusion according to its partition coefficient equilibrium.
While this process has proved generally very successful, it has proved problematic for some volatile, water-soluble flavours. The partition coefficient of some such flavors is such that these materials tend to remain within the wall rather than be absorbed into the oily interior. This leads to a disproportionate amount of substance being trapped within the walls, which in turn leads to a greater volatile loss after recovery of the capsules. Examples of important substances in the flavours field subject to this problem include butyric acid, acetaldehyde, acetic acid, diacetyl, acetoin and furfuryl alcohol.